Current delivery systems for various biologically active compounds do not provide prolonged effects without high doses or frequent reapplication. In addition, topical application of such compounds frequently results in side effects such as irritation or toxicity. The irritation in many cases can rise to the level of pain, e.g., in the case of application of free halogens or alcohols. In addition, carrier systems themselves can create undesirable side effects.
As an example, hand antiseptic agents are designed to remove most transient flora just as plain soaps and detergents do, but they are unable to exert either a persistent or a residual antimicrobial activity on remaining flora. This contributes to making hospital environments very dangerous, especially to patients, because there are no products in general use on the market that allow for both immediate and sustained kill of microbes required to prevent hospital acquired infections. Currently, only superficial cleaning is provided and this is not good enough for the healthcare environment. In part, as a result of this superficial cleaning, it is believed that as many as 100,000 people die each year from hospital acquired infections. There is a danger of infection for every patient that enters a hospital, especially those bound for surgery, because there are currently insufficient reliable means of removing, reducing, and maintaining the reduction of pathogens on the hands of nurses, doctors and surgeons to a degree necessary to entirely prevent infection. Currently accepted methods/standards only require hand hygiene products to achieve a 2-3 log reduction in vivo in order to enter the professional care/healthcare market without considering extended antimicrobial effects. Failure to consider extended effects is at odds with the fact that hospital patients are already not well and generally have depressed immune systems which put them at high risk for infection, and are therefore the population most in need of an effective/reliable pathogen killer.
Alcohol-based hand sanitizers, so far, have been the preferred agents for hygienic, so-called “waterless” hand-disinfection hand-rubs because they seem to offer more convenience than aqueous solutions and because they purport to offer an optimal antimicrobial spectrum (that is, they are active against all bacteria and most clinically important viruses, yeasts, and fungi); no wash basin is necessary for their use, and they can be readily available at bedsides. It has been shown that alcohol-based preparations in general have more rapid action than products containing other antiseptics (e.g., chlorhexidine gluconate or providone iodine), require less time than traditional hand washing, and contribute to decreased infection rates. Furthermore, they are not likely to microbially contaminate health-care workers' clothing; and exhibit rapid action.
However, alcohol-based hand washes have several drawbacks. For one, in some cases frequent hand-washing even with alcohol, may not result in the desired microbial reduction. For example, after performing a vaginal examination, it is recommended to disinfect hands in a chlorinated solution. More importantly, alcohol-based hand sanitizers stop working the instant they dry. That is, as soon as the alcohol evaporates, its anti-microbial activity ceases. In addition, alcohol washes do not exhibit persistence in their anti-microbial activity. Although the leading manufacturer of alcohol-based hand sanitizers claims that their product kills 99.99% of most common microorganisms in as little as 15 seconds, the alcohol-based hand sanitizers dry in 8-10 seconds and fall below the efficacious concentration of alcohol in seconds. Recontamination occurs as soon as the hands come into contact with a contaminated surface. Moreover, recontamination is also likely to occur even before the hands come into contact with a contaminated surface. It is now known that contamination can occur by contact with microbes that are in the room atmosphere.
It has been reported that alcohol-based hand sanitizers offer no residual protection, and that if a user's hands feel dry after rubbing them together for 15 seconds, an insufficient volume of sanitizer was likely applied (e.g., A laboratory model for the investigation of contact transfer of microorganisms, Marples, R. R. & Towers, A. G. The Journal of Hygiene, 82(2), 237-248 (1979); herein incorporated by reference in its entirety). Moreover, gelled alcohol-based hand sanitizers became less effective with repeated use and made the skin dirtier, not cleaner due to removal of protective natural skin oils and entrapment of dead skin cells by the polymer thickeners used in the gelled alcohol-based products. In a referenced study to simulate repeated usage, subject's alcohol-based sanitized hands were repeatedly inoculated with bacteria followed by an application of hand sanitizer, then evaluated for antimicrobial effectiveness. The antimicrobial efficacy of the alcohol-based hand sanitizer showed a markedly decreased antimicrobial efficacy with subsequent contamination and decontamination cycles. In addition to these objective results, subjects were asked to subjectively evaluate the condition of their hands after the completion of the test protocol. 47% of the subjects who had completed the test protocol with the alcohol-based hand sanitizer reported palmar pain or discomfort, and tended to indicate some discomfort in palmar surfaces for one to several days after the test. (e.g., Testing a new, alcohol-free sanitizer to combat infection, Dyer, D. L., Gerenraich, K. B., & Wadhams, P. S., Association of Operating Room Nurses Journal, 68(2), 239-251 (1998); herein incorporated by reference in its entirety).
Thus, in a manner similar to other topically applied active compounds, the desired effects of the active ingredient does not last.
An additional problem with alcohol-based hand wash preparations is the fact that alcohol-based hand wash preparations tend to strip the skin of essential oils and sebum, which is a further undesirable side effect. Moreover, when they are applied to wounds not only do alcohol-based hand wash preparations increase the risk of injury to the tissue of the wound and cause pain, they also form a coagulum under which bacteria may subsequently thrive (e.g., Testing a New Alcohol-Free Hand Sanitized to Combat Infection, Dyer, D. D., Gerenraich, K. B., and Wadhams, P. S., AORN Journal, Vol. 68, No.2, Pages 239-251 (1998); herein incorporated by reference in its entirety). Wearing gloves to prevent re-infection of hands presents similar problems in compliance with hand hygiene. Gloves may be thought of as adding another layer of skin to one's hands, but failure to thoroughly wash gloved hands, remove, or change gloves after each patient or other contaminating contact, results in the same germ transfer problem. Moreover, it is known that many potential glove wearers are allergic to the gloves or the powders used with the gloves.
It can be seen there is a problem in the field in that while many active compounds can be effective, the effectiveness may be transient, e.g., the immediate effectiveness of many of the presently available hand-sanitizers, including soap, detergents, and antiseptic agents, as well as the alcohol washes discussed above, may be acceptable at the time of washing, their effectiveness quickly diminishes in a short time after washing, frequently measured in seconds.
Similar problems, e.g., with sustained effectiveness and side effects arise in other types of dispersions for topical use, e.g., topical analgesics, anti-inflammatories, antihistamines, colorant, keratolytics, etc. and perhaps even for oral use, e.g., a clay loaded with an anti-diarrheal compound, purgative, antacid or antibiotic.
A number of patents address the possibility of causing an antimicrobial compound bound to a substrate to be suspended in water. Specific patents are U.S. Pat. Nos. 6,015,816; 6,288,076; and U.S. Patent Publication 2003/0161866A1; herein incorporated by reference in their entireties. U.S. Patent publication 2003/0161866 recognizes that suspensions in water of ion exchange materials such as clays may be combined with certain ligands. Suspensions as describe in these patent publications are generally of very low viscosity and the publication does not seem to recognize that the compositions they describe simply seem to run from surfaces to which they are applied. While this may be acceptable in non-topical applications where the application can be quickly dried at high temperature, such would not be acceptable in topical applications where skin may not be exposed to sufficiently high temperatures for quick drying. Thus none of the above approaches provide sufficient benefit.